There is an increasing demand for patterned deposition of materials on receivers in traditional image and document printing and upcoming manufacturing applications. These deposition techniques can be broadly classified in non-contact printing systems and methods including, for example, ink jet printing and contact printing systems and methods including, for example, screen printing, flexography, offset lithography, and slot coating.
Ink jet printing has become recognized as a prominent contender in the digitally controlled, electronic printing arena because, e.g., of its non-impact, low-noise characteristics, its use of plain paper and its avoidance of toner transfer and fixing that is required in electrophotography based printing methods. Ink jet printing mechanisms can be categorized by technology as either drop on demand ink jet (DOD) or continuous ink jet (CIJ).
The first technology, “drop-on-demand” (DOD) ink jet printing, provides ink drops that impact upon a recording surface using a pressurization actuator, for example, a thermal, piezoelectric, or electrostatic actuator. One commonly practiced drop-on-demand technology uses thermal actuation to eject ink drops from a nozzle. A heater, located at or near the nozzle, heats the ink sufficiently to boil, forming a vapor bubble that creates enough internal pressure to eject an ink drop. This form of inkjet is commonly termed “thermal ink jet (TIJ).”
The second technology commonly referred to as “continuous” ink jet (CIJ) printing, uses a pressurized ink source to produce a continuous liquid jet stream of ink by forcing ink, under pressure, through a nozzle. The stream of ink is perturbed using a drop formation mechanism such that the liquid jet breaks up into drops of ink in a predictable manner. One continuous printing technology uses thermal stimulation of the liquid jet to form drops that eventually become print drops and non-print drops. Printing occurs by selectively deflecting one of the print drops and the non-print drops and catching the non-print drops. Various approaches for selectively deflecting drops have been developed including electrostatic deflection, air deflection, and thermal deflection.
Micro-Electro-Mechanical Systems (or MEMS) devices are becoming increasingly prevalent as low-cost, compact devices having a wide range of applications. As such, MEMS devices, for example, MEMS transducers, have been incorporated into both DOD and CIJ printing mechanisms to control ink drop formation.
There is a constant need for patterned deposition of increasingly complex liquids using inkjet printing especially in applications for manufacturing of functional devices. Many of these complex liquids are loaded with fine particles and have much higher viscosities compared to typical inks used in inkjet. Thus, these liquids are difficult to eject to form drops. U.S. Patent Application Publications 2010/0238232 and 2010/0188466, both by Clarke et al., show a continuous ink jet system in which a liquid 2 in introduced by an injection mechanism into a liquid 1. Droplets of liquid 2 are formed in liquid 1 and then ejected into the air in the form of encapsulated drops. While this is a good way to create an inkjet system that can eject droplets of, for example, high viscosity inks that are difficult to otherwise eject by encapsulating the hard to jet liquid in another liquid whose properties are better suited to continuous ink jet; there is a need to be able to selectively inject the liquid 2 into liquid 1 so that liquid 2 is ejected only in the locations it is needed.
Contact type printing methods such as screen printing, flexography and offset lithography typically enable deposition of more complex liquids and give a better control on thickness of the deposited layers. These methods suffer from a limitation of no digital control in printed pattern because only fixed patterns can be printed. It is expensive to make changes to the patterns by changing plates or screens. Also, these methods do not allow change of pattern on the fly such as in inkjet printing.
In addition, it has long been known in the art to coat a uniform layer of a liquid by a contact transfer of a bead formed by liquid emerging from a slot die as shown in U.S. Pat. No. 2,681,294. This coating method allows deposition of uniform films having a range of thickness of complex materials. It is also possible to coat multiple layers of different liquids uniformly as shown in U.S. Pat. No. 2,761,791. U.S. Pat. No. 6,517,181 describes a method of coating a mixture of liquids using control mechanisms to control the relative flow of at least of the on liquids to vary the concentration of the mixture to form a pattern when coated on the receiver. Heretofore, however, the coating industry lacked the ability to transfer coat multiple liquids, where at least one of the liquids can be controllably dispersed in a carrier liquid to form discrete drops and to transfer the liquid drops to a receiver to produce a patterned deposition of the liquid.